This invention relates generally to semiconductor manufacture and testing, and more particularly to a method for fabricating and testing semiconductor components.
Photolithography is widely used in semiconductor manufacture and other applications. During photolithography, an exposure energy, such as ultraviolet light, is passed through a mask and onto a target such as a semiconductor wafer. The mask contains opaque and transparent regions which form a primary mask pattern. The exposure energy exposes the mask pattern on a layer of resist deposited on the target. Following exposure, the layer of resist can be developed to form a resist mask. In semiconductor manufacture, such a resist mask can be used for etching, ion implantation, screen printing, CVD and other processes.
One recently developed form of lithography uses a laser scanner to focus modulated laser beams in a series of scan lines onto a radiant sensitive film of resist. This technique eliminates the mask, as the pattern is written directly onto the resist. A conventional laser scanner includes a laser adapted to generate a collimated light beam, that can be split into an array of collimated sub beams. Typically, the laser beam comprises ultraviolet light having a wavelength of 325 nm or 363.8 nm. The laser scanner also includes a modulator, such as an acousto-optic modulator, adapted to receive a data signal in digital form, and to modulate the laser beam responsive to the data signal. In addition, the laser scanner includes scan optics, such as a rotating reflective polygon, adapted to form an image of the beam and to sweep the image across a scan line. The laser scanner also includes a precision stage adapted to move the target in X and Y directions approximately perpendicular to the scan line direction.
The present invention employs a laser scanner and direct laser imaging to improve various wafer level fabrication and test processes for semiconductor components. For example, semiconductor dice, semiconductor packages, and semiconductor interconnects are typically fabricated on a single substrate (e.g., wafer or panel) that is subsequently singulated into individual components. These processes are sometimes referred to as being xe2x80x9cwafer levelxe2x80x9d processes.
One shortcoming of wafer level fabrication processes is that some of the components on the substrate can be defective. For example, defects can occur in the integrated circuits contained on the components, in the address circuitry for the components, or in the configuration of the arrays of semiconductor devices on the components. Some defects can make a component non-functional, while other defects merely affect the electrical characteristics of the component.
The defective components can decrease the yield of the substrate and affect the quality of the singulated components. In addition, the defective components can compromise subsequent test procedures, particularly wafer level burn-in tests. For example, conventional burn-in boards utilize xe2x80x9cshared resourcesxe2x80x9d wherein multiple components are electrically connected in series, and the same test signals are applied to multiple components. Defective components can short the test signals, and adversely affect the test process.
Rather than having specific defects, other semiconductor components can have electrical characteristics that do not meet certain standards. For example, one important electrical characteristic is the speed with which the components process signals. Some functional components can have speed characteristics that make the components unsuitable for a particular application. Again the substandard components can decrease the yield of the substrate.
The present invention utilizes a laser scanner and direct laser imaging to improve wafer level fabrication and test processes for semiconductor components.
In accordance with the present invention, a method for fabricating and testing semiconductor components is provided. Also provided are improved semiconductor components fabricated using the method, and a system configured to perform the method.
Initially, a substrate having a plurality of semiconductor components is provided. For example, the substrate can comprises a semiconductor wafer, or a portion thereof, containing multiple semiconductor dice or semiconductor packages. In addition, the components on the substrate can include component contacts, such as bond pads, in electrical communication with integrated circuits contained on the components.
As a first step, the components on the substrate are tested to xe2x80x9cevaluatexe2x80x9d and xe2x80x9cmapxe2x80x9d the components. The testing step can include xe2x80x9cfunctionalxe2x80x9d tests for evaluating a gross functionality of the components, as well as xe2x80x9cparametricxe2x80x9d tests for evaluating various electrical characteristics of the components (e.g., speed). The testing step identifies and locates both xe2x80x9cdefectivexe2x80x9d components and xe2x80x9cgoodxe2x80x9d components on the substrate.
A metal redistribution layer is then blanket deposited on the substrate, and on the component contacts. Next, a radiant sensitive film, such as a wet film resist, or a dry film resist, is blanket deposited on the redistribution layer. The radiant sensitive film is then exposed using a laser scanner programmed with digital data representative of a desired pattern of conductors. In addition, the digital data includes test data from the initial testing step. Development of the exposed radiant sensitive film forms a mask that can be used to etch the pattern of conductors on each component. Such an etching process is known in the art as a xe2x80x9csubtractivexe2x80x9d process. However, a laser imaged mask can also be used to form the conductors using an additive process (i.e., deposition of a metal through the mask).
The conductors are-configured to xe2x80x9cfan outxe2x80x9d, or other wise locate, terminal contacts for the components in a required pattern, such as a grid array. In addition, using the test data, the conductors can be configured to repair or re-configure selected components, such as defective or substandard components. Alternately, the conductors can be configured to isolate defective components for wafer level burn-in, or to form component clusters configured to improve xe2x80x9cwafer yieldxe2x80x9d by excluding selected components.
As another alternative, using the test data, a matching test board can be fabricated that is configured to electrically engage the good components on the wafer, while the defective components are electrically isolated. The test board can also be fabricated using a laser scanner and a laser imaging process employing essentially the same data used to pattern the redistribution layer.
In an alternate embodiment of the method, a semiconductor package is fabricated with a solder mask, or a rigidifying mask, patterned using a laser scanner and a laser imaging process.